1. Field of Invention
The number of vehicles towing another vehicle has increased considerably over the past two to three decades. A large amount of this increase is due to the influx of recreational vehicles with drivers having little or no experience in towing another vehicle. Laws have been passed requiring towed vehicles exceeding a certain weight to be equipped with a brake system. The brake system must respond with the brake system of the towing vehicle.
In the past a hydraulic coupling device between the towing vehicle and the towed vehicle was used which allowed for the direct transfer of hydraulic fluid and hydraulic pressure between the brake systems of the two vehicles. With the event of the modern computer controlled brake system, in particular the anti locking brake system, such direct transfer of hydraulic fluid and pressure is not desirable.
Other relatively expensive systems utilizing a vacuum or compressed air to activate a hydraulic brake system on the towed vehicle have been developed and are in use today especially on commercial semi-trucks and trailers.
In relatively recent times all electric brake systems have been devised and are on the market today. The all electric brake system utilizes a small computer control unit in the cab of the towing vehicle to emit an electrical impulse when the brake pedal of the towing vehicle is pressed. An electromagnet in the wheel hub of the towed vehicle is energized by the electric impulse from the towing vehicle which in turn magnetically clamps to the rotating wheel hub. The frictional force between the electromagnet and the wheel hub causes the electromagnet to apply a force to a lever system that rotates a cam which in turn expands the brake shoes against the wheel brake drum. While this system is relatively inexpensive and it does not effect the computerized brake system on today's vehicles, it does have several drawbacks. The electromagnet can be rendered useless if energized under water as can be and has been the case on boat trailers. The system inside the wheel hub is subjected to many harsh environments and chemicals. These harsh environments are corrosive causing the need for short inspection intervals followed with proper repairs. The cam mechanism for expanding the brake shoes against the brake drum was used on cars back in the twenties and thirties. Because of the short distance the cam expands the brake shoes they must be manually adjusted frequently.
Another system in use today, especially on boat trailers, is a system called surge brakes. This system provides a master hydraulic brake cylinder as part of the trailer hitch. The hitch is designed to allow the entire towed vehicle to roll forward a few inches when the brakes on the towing vehicle are applied. As the towed vehicle rolls forward a fixed push rod is pushed into the master hydraulic brake cylinder which creates hydraulic pressure to the hydraulic cylinders in the wheel hubs thereby expanding the brake shoes against the brake drums. While this system is relatively inexpensive and does not effect the brake system on the towing vehicle it does have some major drawbacks. Anytime driving conditions are such that the towed vehicle is caused to roll forward and force the push rod into the master hydraulic brake cylinder the brakes on the towed vehicle are applied even though the brakes on the towing vehicle are not being applied. This occurs when the towing vehicle is backing up, especially on a steep grade. A more dangerous situation can happen on a steep down hill grade when the towing vehicle is gearing down to reduce speed causing the towed vehicle to roll forward thereby applying its brakes. This can cause a control problem and seriously overheat the towing vehicle's brakes. Another drawback occurs when the towing vehicle is backing down a grade. In this case the brakes on the towed vehicle cannot be applied presenting the possibility for the towing vehicle to dragged out of control.
2. Description of Related Art
I have diligently searched past patents and have not found a patent relating to an electrical, mechanical system for activating a hydraulic brake system. I have searched the market place and have not found a system on the market that utilizes an electrical, mechanical system for activating a hydraulic brake system.